BACTERIAL ENZYMES 109 



Gram-nepativc forms. Benians*^ has found that crushed Gram-positive bacteria 

 are proni])tly decolorized, indicating that the dye and the cell contents do not 

 form an insoluble comjiound, but that the l)ac"terial cell \vall is the chief factor in 

 detennininK CIram jiositiveness; presumably the iodin renders the cell membrane 

 impermeable to alcohol. This important contribution has been confirmed, as 

 far as the staining of tubercle bacilli is concerned, by Hope Sherman,*" who corrob- 

 orates the finding of Benians that if the bacilli are not intact they are neither acid 

 fast nor (Irani ])ositive. The same is true of yeast cells (Henrici)/' but Dcus^en 

 states that press juice from yeast (Buchncr's zymase) contains Gram-positive 

 £;ranules. 



Bacterial Enzymes^^ 



The metabolic processes of bacteria seem to be closely dependent 

 upon enzyme action, just as with higher cells. Liquefaction of 

 gelatin is a familiar example of the enzyme action of bacteria; and 

 since the filtered cultures of liquefactive bacteria are also capable 

 of digesting gelatin, the enzymes are evidently excreted from the 

 cells. Dead bacteria, killed by thymol or by other antiseptics that 

 do not destroy proteolytic enzymes, will also digest gelatin. Numer- 

 ous investigations have established the wide-spread occurence of 

 many soluble enzymes both in bacteria and in their secretions, indi- 

 cating that bacterial cells are as dependent on enzymes for the pro- 

 duction of their metabolic activities as are higher types of cells, and 

 that these enzj^mes are not only present as intracellular constituents, 

 but that they also escape from the cells. Even the spores contain 

 active enzymes. ^^ A striking property of bacteria is their reducing 

 power, which has led to the introduction of selenium and tellurium 

 salts, which are reduced to the metals, as an index of bacterial life 

 and activity (Gosio). 



The diffusion method of Wijsman, or, as it is more frequently 

 called, auxanogmphic method of Beijerinck, offers a relatively simple 

 means of detecting the presence of extracellular bacterial enzj-mes. 

 Eijkman^" in particular has used this method, which consists of mix- 

 ing agar with milk, or starch, or whatever material is to serve as the 

 indicator of the enzyme action; the agar is then inoculated with bac- 

 teria and plated (or else the bacteria are inoculated as a streak on the 

 surface of the agar) . About each colony there will appear a zone of 

 clearing in the medium if it produces enzymes digesting the admixed 

 substance. By this means Eijkman found that all bacteria that 

 produce enzymes digesting gelatin also digest casein, and those that 

 do not digest gelatin are equally without effect on casein; therefore, 

 it is probably the same enzyme that digests both. As the hemolytic 



65 Jour. Path, and Bact., 1912 (17), 199. 



66 Jour. Infec. Dis., 1913 (12), 249. 

 6^ Jour. Med. Res., 1914 (30), 409. 



68 See Fuhrmann (" Vorlesungen iiber Bakterienenzyme," Jena, 1907) for com- 

 plete bibliography to that date. 



65 Effront, Mon. sc. Quesneville, 1907, p. 81. 

 " Cent. f. Bakt., 1901 (29), 841. 



